.App{
  width: 100%;
  height: 100%;
  background-color: aquamarine;
  display: flex;
}
.left-box{
  width: 200px;
  height: 100%;
  background-color: chartreuse;
  
}
.right-box{
  flex: 1;
  height: 100%;
  background-color: bisque;
}
.left-box li{
  padding-top: 20px;
  text-align: center;
  border: 1px solid #000;
 
}